The invention relates to chains, including the dragline type used in excavations such as strip mining. In particular, the invention relates to an improved dragline chain highly resistant to wear and including links which are separable for replacement of the link pin or the entire link.
A variety of types of dragline chains and links for such chains have been previously suggested. See, for example, U.S. Pat. Nos. 1,836,169 and 2,869,255. Other types of chains are shown in U.S. Pat. Nos. 2,824,421; 3,959,909; 1,512,609; 3,321,907 and 3,958,411.
As illustrated in the first two patents listed above, most dragline chain is formed of inter-engaged loop-like links, each of which is continuous. These chains have usually been made by placing individually cast links in a mold, placing cores around them and pouring the connecting link. This process is very costly as well as creating difficulty in cleaning, heat treating and handling, etc. Also, repair and rebuilding of such chains has been a problem in that an adjoining link can never be moved completely out of the way to weld a worn area. Repairs have often been made using a repair link which is either bolted, pinned, welded or keyed and of a different design from the remaining links, which necessitates the maintenance of additional inventory.
Some chain links of the type having non-integral pins which are assembled into the link and which sometimes may be removed, such as the links shown in the above references U.S. Pat. Nos. 1,836,169 and 3,958,411 have utilized cylindrical link pins which under many circumstances can cause an undesirable type of wear. As the pin wears to a smaller diameter, which sometimes occurs even more readily when the pin is permitted to rotate, the pin eyes tend to become egg-shaped, forming a narrow pocket at the bottom. If the pin is then replaced, the new pin is larger in diameter than the pocket areas, creating a wedging action when the chain is under tension which can quickly snap the ends of the link.
Other dismantleable type chain links, generally not used as original links in dragline chains, have tended to wear undesirably for various reasons. For example, exposed pin ends having rivet heads for maintaining the pin in place are often worn away, leaving the pin free to escape the link. Excessive wear on the sides of the main body of the link has often been a problem, also. None of the chains or chain links used or suggested heretofore has provided the highly wear-resistant, relatively inexpensive, and easily repaired chains, particularly suited for dragline purposes, as does the present invention described below.